The subject matter disclosed herein relates to energy production and, in particular, to direct-fired coal combustion in a gas turbine.
An Integrated Gasification Combined Cycle (IGCC) is a clean coal technology that turns coal into gas—synthesis gas (syngas). It then removes impurities from the coal gas before it is combusted. This results in lower emissions of sulfur dioxide, particulates and mercury. It also results in improved efficiency compared to conventional pulverized coal. Existing IGCC plants entail significant capital equipment to perform coal gasification plus cleanup of the resultant syngas to prevent carryover of particulate matter to the gas turbine.
A fundamental problem is the cost and complexity of an IGCC plant that makes it difficult to compete with conventional coal-fired boilers. The ability to direct-fire coal in a combined-cycle plant will reduce greenhouse gas (GHG) emissions due to higher combined cycle (CC) efficiency. The associated problem is that direct-firing coal in a gas turbine causes significant rates of hot gaspath erosion or deposition and performance degradation.
Ash and noncombustibles in the solid coal fuel are addressed in the conventional IGCC plant via post-treatment and separation equipment, as well as heat exchange with the syngas to reduce its temperature to an acceptable level for the separation equipment. One approach has been to perform staged combustion and particulate separation in silo equipment separate from the gas turbine. Another approach has been to use an offboard fluidized-bed combustor as a gasifier, followed by an onboard lean combustor.